The invention concerns an analytical device which contains a lancet and an analytical test element. The invention also concerns a process for manufacturing such an analytical device.
The examination of blood samples in clinical diagnostics enables the early and reliable recognition of pathological states as well as a specific and well-founded monitoring of physical conditions. Medical blood diagnostics always requires the collection of a blood sample from the individual to be examined. Whereas in hospitals and in doctor's offices several milliliters of blood are usually collected by venepuncture from a person to be examined for analysis in order to carry out many laboratory tests, individual analyses which are directed towards one parameter nowadays often only require blood quantities ranging from a few microliters down to less than one microliter. Such small quantities of blood do not require a laborious and painful venepuncture. Instead it is sufficient to push a sterile sharp lancet into a finger pad or earlobe of the person to be examined to collect blood through the skin and thus to obtain a few microliters of blood or less for analysis. This method is particularly suitable when it is possible to carry out the analysis of the blood sample immediately after blood collection.
Lancets and suitable instruments for them (so-called blood withdrawal instruments, blood lancet devices or—as they are referred to in the following—lancing aids) which enable blood collection that is as pain free and reproducible as possible are available especially for so-called home monitoring i.e. where medical laymen carry out simple analyses of the blood by themselves and are used in particular by diabetics to collect blood regularly and several times daily to monitor the blood glucose concentration. Furthermore the use of lancets with lancing aids is intended to reduce the psychological barrier associated with piercing one's own body which is particularly important for children that suffer from diabetes and need regular blood glucose tests. The commercially available instruments (lancing aids) and lancets Glucolet® from Bayer AG and Softclix® from Roche Diagnostics GmbH are mentioned as examples of lancets and lancing aids. Such lancets and instruments (lancing aids) are for example the subject matter of WO-A 98/48695, EP-A 0 565 970, U.S. Pat. No. 4,442,836 or U.S. Pat. No. 5,554,166.
Personal blood sugar determination (so-called home monitoring) is today a world-wide method in diabetes monitoring. Blood sugar instruments of the prior art such as the Accu-Chek Sensor (from Roche Diagnostics) are composed of a measuring instrument into which a test element (test strip, sensor) is inserted. The test strip is contacted with a drop of blood which has previously been collected from the finger pad by means of a lancing aid. The numerous system components (lancet, lancing aid, test strip and measuring instrument) need a lot of space and require a relatively complex handling. There are now also systems with a high degree of integration which are thus more simple to operate. These for example include the Accu-Chek Compact (from Roche Diagnostics), the Glucometer Dex (from Bayer Diagnostics) and the Soft-Sense (from Medisense). In the two former systems the test strips are stored in the measuring instrument in magazines and are available for the measurement.
A next step in miniaturization is for example to integrate several functions or functional elements into a single analytical device (disposable). For example the operating process can be considerably simplified by a suitable combination of the lancing process and sensory analyte concentration detection on a test strip. There are the following examples of this in the prior art:
EP-B 0 199 484 (Audio Bionics) describes an analytical device (“disposable”; abbreviated dispo) containing an integrated lancet which is actuated by the instrument (see FIG. 9 for example). The lancet is retracted again after the puncture by means of a specific spring mounting (“spring-mounted lance means”). The dispo contains a so-called “wick means” through which the sample liquid is passed from the body surface to the analytical area which is an optically analysable test field.
A method is described in U.S. Pat. No. 6,143,164 (E. Heller & Comp.) in which a body opening (for example a small puncture or incision through the skin) is made and subsequently body fluid is transported into a sensor and examined there for the presence of an analyte. For this purpose U.S. Pat. No. 6,143,164 discloses an analytical device in which a lancing device is attached to a sensor test strip. The sample liquid is transported from the body opening to the actual detection element of the sensor for example again by means of a wick or a capillary gap/channel.
WO 99/26539 (Mercury Diagnostics), U.S. Pat. No. 5,951,492 (Mercury Diagnostics) and U.S. Pat. No. 6,056,701 (Amira Medical) describe, inter alia, collection devices for body fluids comprising an elongate handle; a test field being attached to its head region.
U.S. Pat. No. 6,032,059 (Abbott) and U.S. Pat. No. 6,014,577 (Abbott) describe a disposable containing a needle which is used to pierce the skin. Body fluid which is previously sucked into the needle by capillary action is analysed by a sensor integrated into the needle.
U.S. Pat. No. 5,801,057 (Smart et al.) describes a disposable made of silicon containing an integrated hollow needle. A collection chamber for aspirated body fluid is located at one end of this hollow needle. The concentration of a blood component can be determined in the body fluid by a suitable reaction chemistry.
U.S. Pat. No. 5,035,704 (Lambert et al.) discloses a system for collecting blood containing a magazine for disposables. It is possible to integrate a lancet element into the dispos. A blood drop is transferred to the test field by direct skin contact and can be increased by applying a vacuum.
U.S. Pat. No. 6,132,449 (Agilent Technologies) discloses an integrated dispo with a puncturing and measuring function. The puncturing element is activated perpendicular to the dispo plane whereby it passes through the dispo. The wound opening is in direct contact with several capillary structures which transport the emerging blood into a separate analytical part of the dispo.
A key problem in collecting blood using a so-called “integrated disposable” (in which the lancet and test element are connected together or form a single unit) is the fact that, after puncture, the capillary blood usually does not automatically emerge from the wound. This adverse effect is increased by directly contacting a disposable with the wound opening. After a puncture the blood drop must be actively conveyed to the skin surface by for example mechanically opening the wound and/or applying gentle pressure to the tissue around the wound area (for example by simple “finger milking”). Application of a vacuum can assist this process.
Experiments in the laboratory have shown that it is advantageous to keep the wound open during the period of blood collection. However, this fact results in a complicated movement process of the dispo since a very rapid piercing motion and a slow blood withdrawal movement can only be achieved with a waiting time in the system. Only a few of the dispo designs proposed in the prior art are suitable for this.
A rigid protruding lancet tip has a tendency to cause unintentional injury when collecting the blood drop. Hence a lancing device which moves relative to the disposable is preferable. However, this requirement in combination with the dispos known in the prior art leads to a complicated and thus expensive dispo design.
A further difficulty with known dispos is to ensure the sterility of the lancet for the period until it is used. In the prior art it is known that the tip can be protected by a cap which is manually removed before use. However, such a cap impairs the automation of blood sugar measurements. Previously described concepts which would in principle enable an automated blood sugar determination with an integrated disposable have the disadvantage that there is a latent risk of contaminating the lancet needle tip. Components of the test field (chemicals, biological components, adhesives etc.) can migrate within the dispo via the air or over the surfaces. Thus a sterilization of the needle tip carried out initially is in no way sufficient without further protective measures to meet the requirements for a sterile medical product.
The lancets of the prior art usually have a metal lancet needle with a tip which can be optionally ground. In order to facilitate the handling of the lancet and optionally to attach it in a lancing device, a plastic lancet body made of a rigid, injection-mouldable material is usually injected onto the lancet needle in many embodiments. In the unused state the tip of the lancet needle is surrounded by a protective covering to ensure its sterility. This is usually composed of the same rigid material as the actual lancet body and usually forms one unit with this body. The protective covering can be separated from the lancet body before using the lancet and removed from the tip of the lancet needle. For this purpose there is usually a weakened point between the lancet body and protective cover. After the lancet has been used, the tip of the lancet needle is unprotected and is hence a potential source of injury to the user and possibly to other persons.
The object of the present invention was therefore to eliminate the disadvantages of the prior art and in particular the disadvantages mentioned above. In particular the object of the present invention was to provide analytical devices (synonymous with “disposables”, abbreviated: “dispos”) which do not have the disadvantages of the prior art. In particular the dispo according to the invention should ensure the sterility of the lancets until they have been used while simultaneously integrating the lancet and test element (test strip, sensor). Of course it is also intended to describe a manufacturing process for such analytical devices. Another object of the present invention is to provide analytical devices containing lancets in which at least the lancet needle tip is kept sterile, i.e. germ-free, in the unused state until immediately before use and which can be stored hygienically in the used state. This object should be ideally achieved without the user having to employ separate measures for the hygienic storage. Moreover the user should be protected from accidental injury by the lancet and in particular by the used lancet. Finally it should be preferably possible to simply transfer the sample from the site of blood collection to the site of blood examination.
This object is achieved by the subject matter of the invention as characterized in the individual patent claims. Preferred embodiments are the subject matter of the dependent claims.
A first subject matter of the invention is an analytical device which contains a lancet. The main components of the lancet are a lancet needle with a tip and a lancet body that completely surrounds the lancet needle at least in the region of the tip. The lancet needle can be moved relative to the lancet body. The lancet body is composed of an elastic material at least in the region of the tip of the lancet needle in which the tip of the lancet needle is embedded. The analytical device additionally contains an analytical test element which is permanently attached to the lancet body.
Another subject matter of the invention is a further analytical device which contains a lancet. The lancet in this case comprises a lancet needle with a tip and a lancet body which is in the form of a hollow body in the region of the tip of the lancet needle and which surrounds the tip of the lancet needle. In this case the lancet needle is also movable relative to the lancet body. The hollow body is composed at least partially of an elastic material which can be pierced by the tip of the lancet needle during the lancing process and after retraction optionally reseals the tip of the lancet needle in the hollow body. The analytical device additionally contains an analytical test element which is permanently connected to the lancet body.
Finally the invention concerns a process for manufacturing such analytical devices.
The object of the invention is preferably composed of a miniaturized dispo which combines the three functions of puncturing, blood transfer from the wound generated by the puncturing to the test element and sensor in one element.
The main body of the analytical device according to the invention is composed of a rigid plastic body whose external shape is preferably adapted for the purpose of holding it in an instrument. A lancet needle is embedded in this plastic in such a manner that its tip preferably does not protrude beyond the front edge of the main body. The main body can therefore also be referred to as the lancet body. In the preferred embodiment the main body has ridges which are used to fix the needle in the main body and to guide it during the lancing movement. However, most of the needle is preferably not attached to the main body in order to reduce the frictional force during the lancing movement. The contact surfaces between the needle and lancet body are preferably kept to a minimum and suitably pretreated, for example siliconized.
The lancets according to the invention are preferably designed to be used once and can therefore be referred to as single-use blood lancets or disposable blood lancets. The lancet of the invention comprises a needle (lancet needle) with a tip. The needle is usually several millimeters (mm) to a few centimeters (cm) in length and has an elongate shape. Needles are typically cylindrical since this needle shape is particularly easy to manufacture; however, other needle shapes are also possible. The tip region of the needle comprises the needle tip which is inserted into the tissue when the lancet is used correctly. Consequently the tip of the lancet needle is that part of the lancet which comes into contact with the skin of the individual to be pricked which optionally injures the skin and thus causes a body fluid and in particular blood or interstitial fluid to flow out.
The tip of the lancet needle can for example be rotationally symmetrical which is generally the case for pins. However, it has also proven to be advantageous to provide the needle tip with one or several ground surfaces. The resulting edges which make an angle with the longitudinal axis of the needle and converge in a tip act as a sharp cutting edge during lancing and make the puncturing process less painful than is the case with rotationally symmetrical needles.
The lancet needle of the lancet according to the invention is manufactured from a material which is sufficiently rigid to withstand mechanical strain during the lancing process, the processing steps or other strains which may occur without deformation. The material must also be such that no particles break off or become detached during the lancing process. Finally the needle material must also be sufficiently machinable to enable the needle tip to be sufficiently pointed and the edges of the needle to be ground adequately sharply. Very suitable materials for the lancet needle are above all metals and in particular high-grade steels. However, needles can also conceivably be made of silicon, ceramics or plastics. High-grade steel needles are particularly preferred.
In one embodiment of the invention at least the tip of the lancet needle of the lancet according to the invention is surrounded by the lancet body. In this connection it is important that the lancet body is composed of an elastic material in the region of the tip of the lancet needle. At least the tip of the lancet needle is completely surrounded on all sides by this elastic material i.e. it is embedded in it and thus sealed from the environment. The elastic material of the lancet body, which in the various embodiments can completely or only partially form the lancet body, is characterized in that it is soft, deformable and can be pierced by the tip of the lancet needle without damaging the tip. During the lancing process the lancet needle is moved along its longitudinal axis relative to the lancet body and its tip emerges from the lancet body in order to pierce the skin of the individual to be examined for blood collection. A further important and preferred property according to the invention is that the elastic material optionally again makes a tight seal around the tip of the lancet needle when the lancet needle is retracted into the lancet body. After the lancing process the lancet needle is moved in a preferred embodiment into its initial position relative to the lancet body by reversing the movement of the lancing process and in this position the tip is again completely enclosed on all sides by the elastic material of the lancet body.
The elastic material of the lancet body which completely encloses the tip of the lancet needle ensures the sterility of the lancet needle tip before use, preferably until immediately before use and optionally ensures a hygienic enclosure of the lancet needle tip after use. The term “hygienic enclosure” means that biological material (tissue, body fluid) which may adhere to the needle after the puncture is essentially encapsulated by the elastic material. This prevents especially germs and infectious material from reaching the environment or at least greatly reduces this risk. Consequently the elastic material is impervious to germs and thus prevents their penetration or escape depending on whether the lancet needle is unused or used. In addition the elastic material represents a mechanical protection for the lancet needle tip and thus also prevents accidental injury on the lancet needle tip.
Rubber, caoutchouc, silicone, elastomers and in particular thermoplastic elastomers have proven to be suitable as an elastic material for the lancet body of the present invention. These have properties that are important for the present invention: they are soft, deformable, can be pierced by the lancet needle without damaging the tip and make a tight seal around the used lancet needle tip. Furthermore they can be used for injection moulding processes which allows a mass production of lancets in large numbers.
Thermoplastic elastomers which are also called elastoplasts or thermoplasts or thermoplastic caoutchoucs ideally combine the handling properties of elastomers and the processing properties of thermoplasts. Thermoplastic elastomers are for example styrene oligoblock copolymers (so-called TPE-S), thermoplastic polyolefins (TPE-O), thermoplastic polyurethanes (TPE-U), thermoplastic copolyesters (TPE-E) and thermoplastic copolyamides (TPE-A). In particular thermoplastic elastomers based on styrene-ethylene-butylene-styrene-polymers (SEBS polymers, e.g. Evoprene® from Evode Plastics or Thermolast K from “Gummiwerk Kraiburg GmbH) have for example proven to be particularly suitable.
During the lancing process the lancet needle is moved relative to the lancet body. The latter is preferably held in its position by the lancing aid or lancing instrument during this process. The lancet needle can be specially shaped for the purposes of the drive mechanism and for example have a needle head at the end opposite to the tip or have another lancet body in addition to the lancet body which encloses the tip and can be engaged by a drive element of the lancing aid. The shape of the needle or of the additional lancet body can interact in a suitable manner with a corresponding drive device in the lancing instrument (lancing aid). Such means can generally be referred to as a thickening of the needle.
In order to achieve the advantage that the lancet needle tip is enclosed in a sterile manner before use by the elastic material of the lancet body and is hygienically surrounded by the elastic material after use, it is of course necessary that the lancet needle is moved back after use, i.e. after the lancing process, essentially into its original position relative to the lancet body containing the elastic material. This can be achieved by suitable interaction with a correspondingly adapted lancing aid. It is only important that, after use, the lancet needle tip is again enclosed by the elastic material of the lancet body which thus prevents accidental injury on the needle tip.
In order to increase the stability of the elastic material it is possible to combine it with a stiff material, for example a stiff plastic material. For example the outside of the elastic material which does not come into contact with the tip of the lancet needle can be stabilized with a layer of a stiff material, for example a stiff plastic. It is also possible to manufacture the lancet body from elastic material only in the region of the lancet needle tip and to manufacture the remaining lancet body from conventional stiff plastics. In this case the elastic material and the stiff material can be glued together or joined together by an injection moulding process, for example a two component injection moulding process. The stiff material of the lancet body ensures the mechanical stability of the elastic material during the lancing process and facilitates the immobilization of the elastic part of the lancet body during the lancing process by the lancing aid. The stiff material can also be a part of the test element, for example a capillary gap test element as described in WO 99/29429.
In a further embodiment of the invention the lancet contains a lancet needle with a tip and a hollow body which surrounds at least the tip of the lancet needle, the lancet needle being movable within the hollow body in the region of its tip and the hollow body being at least partially composed of an elastic material that can be pierced by the tip of the lancet needle during the lancing process and which optionally reseals the tip of the lancet needle in the hollow body when it is retracted.
Whereas with the lancet described further above according to the first embodiment, the region of the tip of the lancet needle is completely surrounded on all sides by an elastic material and thus without any remaining hollow space around the tip to ensure sterility before use and hygienic shielding after use, in the second embodiment described above the tip of the lancet needle is surrounded by the hollow body which is closed on all sides. The areas of this hollow body which do not come into contact with the lancet needle are preferably manufactured from a stiff material and preferably an injection mouldable material. It is important for the invention that the area of the hollow body which is pierced by the lancet needle tip during the lancing process is composed of an elastic material.
During the lancing process the lancet needle is moved relative to the hollow body which represents the lancet body. The holder and drive for the lancet needle and attachment of the lancet body can be achieved by suitable constructional measures in the lancing aid as described above.
The elastic material which comprises a part of the hollow lancet body is pierced by the lancet needle tip during the lancing process and optionally reseals after the lancet needle tip is retracted into the hollow body and thus seals the hollow body. Hence the lancet needle tip is thus aseptically sealed in the hollow body immediately before use and is hygienically enclosed in it after use.
The lancet of this embodiment can, like the lancet of the alternative inventive embodiment described above, also have an additional lancet body in addition to the lancet body which encloses the tip of the lancet needle which interacts with suitable elements of a lancing device during the lancing process. In addition the lancet needle can have a special shape, for example have a head at the end opposite to the tip.
With regard to the properties of the elastic material and the joining of the elastic material with the stiff material of the lancet body the same applies as that already mentioned above with reference to the first embodiment.
The blood transfer from the wound/puncturing site of the lancet to the measuring site is achieved according to the invention by two basically different methods: On the one hand the operator of the analytical device can manually transfer the blood drop obtained after the lancing process onto the corresponding test element. However, the blood transfer is preferably achieved “automatically” without any assistance by the user of the dispos according to the invention. For this purpose the dispo can have means for sample liquid transport. These means are preferably capillary active, for example in the form of a gap or a channel in a rigid main body or absorbent matrix materials. It is also possible to combine these two basic methods for example in that the blood is firstly transported through a capillary channel, taken up by an absorbent matrix material and dispensed onto a test element.
Fleeces, papers, wicks or fabrics have proven to be particularly suitable as absorbent materials in the sense of this invention.
In a preferred embodiment the main body (lancet body) of the analytical device contains the means for sample liquid transport. This may be an absorbent wick recessed into the lancet body or preferably a formed capillary gap which is located directly next to the needle and has an inlet in the proximity of the needle outlet. As a result the dispo does not have to be laterally moved for blood collection (or only slightly). The geometry of the inlet opening is designed such that the blood drop that forms can collect there as easily as possible and has for example a funnel or notch shape. The capillary action then ensures that the required amount of blood, which can be considerably below 1 microliter, is aspirated. By this means the blood reaches the test field and reacts there with the test chemistry to generate an analysable electrical signal or colour change. The capillary gap can be moulded into the plastic during the injection moulding or be subsequently introduced into the plastic body for example by embossing or milling.
In another preferred variant the means for sample liquid transport (e.g. a capillary gap or a wick) is not moulded into the plastic which forms the lancet body but is produced by the specific structure of the test element. For example the test element can have a structure similar to WO 99/29429 or EP-A 0 359 831.
The methods known in the prior art are used for the sensory detection of the analyte in particular of blood glucose. Photometric and electrochemical methods are preferred.
The analytical test element of the inventive analytical device can be composed of a detection film which is directly joined to the lancet body. Such detection films are known in diverse embodiments from the prior art. For example such a detection film is described in WO 99/29429. Furthermore, as already mentioned above, a complete conventional test element can be joined to the main body/lancet body of the device according to the invention. Such test elements are also known to a person skilled in the art.
The test element can be joined to the lancet body in many different ways. These include but are not limited to, gluing, welding, clipping, attachment via Velcro fastening or magnets, sewing, screwing and such like. The test element is preferably glued to the lancet body for example by means of hot-melt adhesive or by means of a double-coated adhesive tape.
In general the operation of the disposables according to the invention can be described as follows:
1. The dispo is inserted into the holding device of a (blood sugar) measuring instrument and is attached there.
2. The drive mechanism of the lancing unit is tensioned and coupled to the needle thickening of the dispo.
3. When the lancing process is actuated, the needle is moved forwards and in this process emerges at high speed from the soft plastic. The entire lancing process only takes a few milliseconds.
4. After the skin has been punctured the needle is retracted again into the soft plastic (initial position). The drive is optionally disengaged.
5. After a suitable drop of blood has formed, the entire collection device is moved forward until the suction opening (e.g. capillary) contacts the drop. Alternatively the blood drop can be manually applied to the appropriate sample application zone of the test element.
6. In the variants of the disposable which have means for sample liquid transport, the suction action of these means transports the blood in the dispo to a site where a signal is generated by means of a photometric or electrochemical reaction which depends on the concentration of the blood component.
A disposable according to the invention can in principle be manufactured by the following simple steps:
(1) Injection moulding the main body including embedding the lancet needle (optionally with generation of the “needle head” i.e. a thickening that can be engaged by a lancing instrument)
(2) sheathing the needle tip with soft plastic
(3) sterilizing the “crude disposables” (which are essentially composed of the lancet optionally together with a capillary channel in the lancet body) for example by means of gamma radiation
(4) test assembly i.e. connecting the test element with the main body.
Preferably the “crude dispos” as well as the test elements can be present as a tape material which is separated into the individual dispos after the test assembly for example by cutting or punching. Irrespective of whether the disposables according to the invention are manufactured as rolls or tape material in a continuous process or batch-wise or individually, it is important that the lancet and test element are not joined together until after the lancet needle has been sterilized. A sterilization of the disposables after final assembly could result in damage to sensitive chemical or biological substances in the test field. This can be avoided by the process according to the invention.
Finally a subject matter of the invention is the use of an elastic material as a component of a lancet of an analytical device where the elastic material maintains the sterility of at least the tip of a lancet needle in the unused state. In a preferred embodiment the elastic material can also be used to hygienically shield at least the tip of the lancet needle in the used state.
The use according to the invention of an elastic material to shield the tip of the lancet needle ensures the sterility of an unused lancet needle tip and optionally hygienically shields the used lancet needle tip.
The lancet needle tip can be sterilized in the unused state by suitable measures such as for example gamma radiation. Once sterilized the lancet needle tips remain sterilized by the corresponding lancet body which includes an elastic material. In contrast to the prior art where no elastic materials for shielding lancet needle tips have been described, the use of the elastic material according to the invention also enables the hygienic screening or shielding of the used lancet needle tip. The use of the elastic material allows resealing of a channel which may be present for a brief time through which the lancet needle can pass for the purposes of lancing after the lancet needle has been retracted i.e. after completion of the lancing process. Hence contaminants, in particular germs and infectious material which may adhere to the lancet needle tip after the lancing process cannot reach the environment or only to a limited extent. This is of particular advantage for disposable lancets which are individually disposed of after use. This property is, however, of outstanding importance for sets of lancets and lancet magazines in which used lancets are stored next to unused lancets which can then be disposed of as a whole.
The invention has the following advantages:                The tip of the lancet needle is shielded germ-tight in the unused state in all embodiments i.e. germs cannot reach the lancet needle tip until immediately before using the lancet. After suitable sterilization the lancet tips remain sterile for a long period.        The sterility of the lancet needle is also ensured in the subsequent manufacturing steps such as the joining of lancet and test element. In this process the sensitive needle tip is protected from mechanical influence (bending etc.).        In all embodiments the tip of the lancet needle can be hygienically screened in the used state. An accidental contamination of the surroundings (user, objects, other lancets) is substantially excluded.        The user of disposables according to the invention is protected from accidental injury on a used lancet needle. The same of course also applies to other persons than the actual user.        The disposables according to the invention can be manufactured cost-effectively in large numbers using conventional injection moulding processes.        The disposables according to the invention can be miniaturized to a substantial degree and are therefore suitable for use in compact automated systems.        All previously known variants of test strips and sensors can be used as analytical test elements.        